Oil-bearing vegetable matter, especially oil fruits such as olive meat or flesh, and oil-bearing seed such as sesame seed, sunflower seed and soy beans can be cleaned, treated mechanically and thermally, prepressed and finally extracted to recover a large portion of the material oils (edible oils) therefrom.
The mechanical and thermal treatments, known as conditioning are generally carried out in two separate steps. In a first step a precomminution is effected so that the cellular matter which contains the oil is broken down. The apparatus used for this purpose can include fluted or grooved drums or rollers and flaking drums.
The second step follows the mechanical conditioning and involves a thermal treatment in which the vegetable matter is moistened as required, preheated and dried in conditioning drums or heating trays. Only thereafter is the oil-bearing seed or meat prepressed to remove part of the oil, the balance being recovered by the solvent extraction thereafter.
The earlier system not only has the disadvantage that the comminuting devices are subjected to a high degree of wear and in many instances are detrimental to an effective oil recovery, but also that the numerous successive steps require a large transport path for the vegetable matter which in itself may cause deterioration of the product.
Furthermore, the heating devices usually require agitators or turners for the vegetable matter which consume energy and must be continuously monitored so that the plant occupies considerable space and requires attendance of a large staff for effective monitoring.
There have been attempts to overcome these disadvantages. For example, in German patent documents (Printed Application - Auslegeschrift) DE-AS No. 2,335,385 (see U.S. Pat. No. 4,024,163) there is described a process in which the oil-bearing fruit and oil-bearing seed is conditioned in the absence of air thermally and mechanically in a single process step.
For this purpose, a worm or screw press is utilized. Although this system affords a significant energy saving, the overall energy consumption of oil recovery by this process is still excessive, particularly in these days of significant concern for energy conservation.
It has already been proposed to provide direct extraction of the vegetable matter. For example, in German patent document (Open Application - Offenlegungsschrift) DE-OS No. 24 53 911, a prepressing of the oil-bearing material is omitted although, to reach a high degree of oil recovery and a minimal oil content in the residue after extraction, it is necessary to transform the vegetable matter into especially fine flakes. For example, for sunflower seed the subdivision must be three times greater than is otherwise the case. The intermediate products frequently must be moistened and dried during their movement through the system. Furthermore the larger amount of oil increases the subsequent distillation costs and requires a three-fold larger apparatus with three times the energy requirement.